1. Field of the Invention
The invention relates to a zoom lens having a small-sized, compact structure and a high zooming rate.
2. Description of the Related Art
Imaging optical devices such as digital still cameras (DSCs), digital camcorders, or the like, including a solid state imaging device such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) that converts an optical image into an electrical signal, are widely used.
Imaging devices need to have a large number of pixels and thus photographing lenses, in particular, zoom lenses with excellent imaging performances are required to meet the imaging devices with a large number of pixels. In addition, the zoom lenses should have a high zooming rate, i.e., 10 times or greater, a wide viewing angle, etc. Also, portability of the imaging optical devices becomes more important, and various designs to meet demands for zoom lenses having high imaging performance, small size, and light weight have been proposed.
Conventional zoom lenses including first through fourth lens groups as seen from an object to be photographed and respectively having a positive refractive power, a negative refractive power, a positive refractive power, and a positive refractive power have been widely used. Also, research on designs of zoom lenses having a high zooming rate, good aberration correction, and a small size has increased.